Grouse louse fairly common

There have been reports of grouse louse being found in grouse harvested in the Northwoods this fall. The look of these flies can be a bit off-putting to grouse hunters, but there is no real cause for concern, according to Department of Natural Resources ruffed grouse specialist Alaina Roth.

Grouse louse are in the family Hippoboscidae. This family is more commonly known as “louse flies,” or “keds.” It has been said that these parasites are likely more familiar to ornithologists (and birders), sheep ranchers and equestrians than to mane entomologists who actually study insects.

All hippoboscid flies feed on blood. These flies can fly, but they tend to stay very close to their host. If one should fall off of its host, it will quickly fly back to that same host, or to the closest available host. Species of louse flies that are found on sheep are never found on birds, and vice versa. Many, such as the grouse louse, have an affinity for a particular species of bird. Over 75 percent of the more than 200 species of Hippoboscid flies parasitize birds. They can be found on birds as small as swifts and on birds as large as the albatross. 

One issue with these parasites is their ability to move from one host to another. While this provides them with the blood they need to survive, it can also mean they can be a vector for pathogens such as avian flu. 

However, according to Roth, they should not be seen as any more of an issue than any other insect or parasite such as mosquitoes or ticks. Grouse, in particular, have proven to be fairly resilient when it comes to diseases of all sorts.

“Our West Nile virus study we conducted for several years showed evidence that grouse are subject to many different diseases but many have the ability to develop antibodies and clear the disease from their bodies going on to live healthy lives, not dissimilar to us when we get a cold and then get better,” Roth said.

Providing high quality habitat is always key for keeping any species healthy, she added. This also helps them recover more quickly when they do get sick. 

“Going back to my analogy of us getting a cold, someone who is safe and cozy in their home with chicken soup and Gatorade will recover much faster than someone who is camping in the woods and just trying to stay warm.,” she explained. “A grouse with good habitat and access to food and resources will fare much better to any stressor, including climate, predators and disease compared to a grouse in poor quality habitat.”

The life cycle of these parasitic flies is rather interesting. While most flies hatch eggs that then hatch into larva or maggots, which then go through a number of instars, or stages, before becoming an adult, these flies have a pupa stage. Females lay a late-stage larva enclosed in a shell that quickly develops into an actual pupa. For those Hippoboscids with bird hosts, the mother often deposits pupae into the roosting site or nest of the host bird. From there, the new adult fly can easily find a host once it emerges. The process takes a great deal of energy on the part of the mother. She carries the larva with her, attached to her uterus, until it is full grown and ready to pupate. The weight of her offspring, and the shell surrounding it, can often exceed the weight of the mother herself.

Hippoboscid flies do not parasitize humans, which is good news. An experiment was done in an attempt to discern if these parasites would bite humans, given the presence of no other host. In the end, the flies did decide to try humans, leaving itchy bite marks, but only in the controlled environment when they were left with no other choice. In G. Robert Coatney’s 1931 study, where he actually convinced two of his friends to play along as hosts to a species of these flies, it was found the flies would not reproduce, nor would they live long. 

These flies are relatively flat, making them more difficult to swat at and kill than an average house fly, for instance. 

Roth stated grouse louse are fairly common, although they are “a real pain” to hunters trying to clean these birds, as the flies burrow under the birds’ feathers. She said the presence of these flies is nothing to be too concerned about. The meat from birds with these parasites on them is still safe to consume. However, as with any other animal, as a safety precaution, a grouse showing signs of sickness should not be consumed.

Beckie Gaskill may be reached via email at [email protected].